The northeast coast of Robbins Island is dominated by the 9 km long Back Banks barrier and beaches (RI 4 and 5). The main beach (RI 4) commences on the southern side of Mosquito Inlet as a low bare sand spit fronted by the 600 m wide tidal sand shoals. It curves to the southeast for 6.7 km, terminating at the base of 40 m high Little Bluff, the sand continuing on to beach RI 5. The beach is one of the longest and most exposed on the west north coast and is backed by a large inner and outer barrier. It faces northeast exposing it to all north through easterly wind waves which average about 1.5 m and maintain a continuous double bar system (Fig. 4.209) for 7 km from the inlet to Little Bluff. The double bar consists of an inner bar usually crossed by westerly skewed rips spaced every few hundred metres and a dissipative outer bar located up to 400 m offshore. The outer barrier consists of a 500 ha well developed transgressive dune system between the inlet and bluff, with 10-30 m high hummocky dunes extending up to 500 m inland and including some active blowouts. The barrier is backed by the inlet in the north and the Eel Creek wetland in the south. This outer barrier is in turn backed by the most extensive inner barrier beach-foredune ridge system in Australia, locally known as the Remarkable Banks. Commencing on the southern side of Eel Creek 120 ridges occupy 1,500 ha and extend for 7 km to the southwest, narrowing from 3 km in the north to 100 m in the south. The ridges fill a V-shaped valley bordered by 50 m high White Rock Ridge to the east and a low wetland to the east. They are probably Pleistocene in age and deposited at a slightly higher sea level. read more

Beach Length: 6.7km